Deciding which deadlift to do comes down to personal preference and how flexible you are. Also, most people don’t feel comfortable with stiff legs for fear of a knee injury. Well, I can assure you if done properly each exercise is completely safe and targets both the glutes, hamstrings, and spine erectors very well. I personally feel like I get a better burn in my hamstrings with the stiff-leg deadlift and usually stick with that if my goal is to work my hamstrings. On a side-note, the Romanian deadlift is a great exercise if your goal is to also work on your hip extension to become better at regular deadlifts as well as squats.